When I import to unity I my model gets divided in many mesh parts. Althought Its only one object/mesh
Unity needs to split up your meshes when a certain vertex count is reached (65535 vertices). By the huge number of splits you got, I'd guess that you have an extremely high vertex count in your scene. Check if you still have subsuf modifiers on your objects and remove them before you export to unity. Could you show a wireframe?



Edit
After seeing your wireframe: it is definetely the vertex count, parts of your mesh are waaay too dense. I dropped in some circles, where the problem is most obvious, but all other parts are too dense as well. Google images for "game topology" to get an ideo how "simple" a mesh should look like, for sufficient performance. All details are usually added via texture and normal-maps. I'd recommend that you use your current model for retology and recreate it with fewer faces. The vast majority of your geometry doesn't conribute to the shape of your model, so you don't need it. Next time, save a version before you aply any modifiers, and in general: be careful with the subsurf. Insteady, add geometry, by hand where it's needed.